Process for coating a substrate with copper oxide and uses for coated substrates

ABSTRACT

Processes for coating substrates, in particular substrates including shielded surfaces, with copper oxide-containing coatings are disclosed. Such processes comprise contacting a substrate with a copper oxide precursor, preferably maintaining the precursor coated substrate at conditions to equilibrate the coating, and then oxidizing the precursor to form a substrate containing copper oxide. Also disclosed are substrates coated with copper oxide-containing coatings for use in various applications.

RELATED APPLICATIONS

This application is a continuation in part of application Ser. No.621,660 filed Dec. 3, 1990 now U.S. Pat. No. 5,204,140 which applicationin turn is a continuation-in-part of application Ser. Nos. 348,789 nowU.S. Pat. No. 5,167,820; 348,788 U.S. Pat. No. 5,039,845; 348,787 and348,786, U.S. Pat. No. 5,182,165 each filed May 8, 1989, each of whichapplications is a continuation-in-part of application Ser. Nos. 272,517abandoned and 272,539 abandoned, each filed Nov. 17, 1988, each of whichapplications in turn, is a continuation-in-part of application Ser. No.082,277, filed Aug. 6, 1987 (now U.S. Pat. No. 4,787,125) whichapplication, in turn, is a division of application Ser. No. 843,047,filed Mar. 24, 1986, now U.S. Pat. No. 4,713,306. Each of these earlierfiled applications and these U.S. Patents is incorporated in itsentirety herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a process for coating a substrate. Moreparticularly, the invention relates to coating a substrate with anelectrically conductive copper oxide-containing material, preferably anelectrically super conductive copper oxide-containing material. Moreparticularly, this invention relates to a new process for producing thinand thick superconductor films.

A number of techniques may be employed to provide conductive copperoxide coatings on inorganic substrates. For example, a high temperaturesintering process may be employed. This process comprises contacting asubstrate with an oxide source comprising for example a copper-oxidecomponent, a yttrium oxide and barium oxide source material andcontacting the components with an oxygen-containing vaporous medium atsintering temperature conditions effective to form the conductive copperoxide coating on the substrate.

However, superconductor materials are very difficult to work with,especially because of their brittleness. Once the material has undergonethe sintering process, it is very difficult to from the material,particularly since the material is usually a ceramic typical of mostsuperconductors.

Such superconducting materials in their finished states are extremelybrittle, unmachineable and unbendable. Whatever form they are in aftersintering is the form they stay in and little or no alterations havebeen developed.

Conventional superconducting materials, such as niobium-titanium andniobium-tin operate at liquidhelium temperatures (4.5 Kelvin) forcooling. New superconductors, currently under development, operate inliquid nitrogen, i.e. an expensive cryogenic fluid, at temperatures of77 Kelvin or higher.

Conventional processing of copper oxide conductors, particularly forsuperconductors include:

(1) Substrate depositions, where ion beams are used on zirconium andsapphire substrates in various types of atmospheres. This method ispresently being developed for microprocessor applicable films. A film isplaced on to the flat surface, (not on a three dimensional surface) of amicroprocessor ship; (2) Fiber (whisker) growth methods, which producepure superconductor fibers using a laser heated growth method; and (3)extrusion.

A limitation of substrate deposition is the high cost of processing andexpensive equipment required, i.e., sapphire substrates, ion beamdeposition furnaces, lasers. However, the prior superconductor processesare still in an early stage of development due to the recent discoveriesin copper oxide based superconductor.

One process undergoing development for applying a superconductor layeror material onto a copper wire, includes surrounding a copper wire witha yttrium-oxide and barium-carbonate powder pack. The powder is firedsimilar to other conventional methods of processing of bulksuperconducting material.

During the process, the outer layer of the copper wire is oxidizedproducing a copper oxide layer around the wire. The yttrium and bariumcomponents react with this copper oxide by diffusion to produce asuperconducting compound, a layer or an outer coating.

The results published to date showed a 5- to 10-micron layer (dependingon firing time) of material in which all three of the constituentelements were present, as observed on the copper wire by a scanningelectron microscope. Whether or not they were present consistently andcontinuously in the appropriate crystal from was not determined, but theEnergy Dispersive Analysis indicated a correct element ratios.

It was also observed that the material could possibly be in patches orthe crystals slightly removed from each other, thus disabling acontinuous circuit. SEM analysis revealed the porous nature of theceramic material and the agglomerated, grainy mix of the various phaseswithin the material.

The conventional ceramic processing techniques have been adopted toprepare kilogram size powder batches and to fabricate bulksuperconductors. In most cases, yttrium oxide, the oxide, peroxide,hydroxide or carbonate of barium and the oxide or carbonate of copperare used as precursors for the YBa₂ Cu₃ O_(x) compound. Appropriatequantities of these precursor powders are mixed effectively by ballmilling. Carbonates and oxides of yttrium, barium and copper have littlesolubility in water and are readily mixed in an aqueous vehicle.

Calcined powders can be formed into different shapes and configurationsby various forming techniques including dry pressing, tape casting,screen printing and extrusion. The dry pressing method has been used tofabricate bulk superconducting parts with dimensions ranging from 90.1to 20 c.m. Superconducting wires have been prepared by extrusionSuperconducting ceramic tapes (-20 to 100 um thick) have been preparedby a tape casting technology similar to that used in fabrication ofmultilayer ceramic capacitors and ceramic packages for integratedcircuits. Layers of superconducting and insulating tapes can belaminated to form multilayer device structure. Superconducting lines andpads have been prepared by the screen printing process. A viscous pasteis first formed by mixing a superconducting powder with organic binders.The paste is then printed through a patterned finemeshed screen onto asubstrate to form thick film superconducting patters having -5 to 20 umthickness.

The formed superconductor parts and circuit patterns are then fired at900°-1000° C. to densify the ceramic. Later, proper oxidation anneal isusually necessary to provide a sufficient oxygen content for therequired superconducting device properties.

Some factors are known to contribute to a better superconductingmaterial and these factors include a higher density resulting inimproved mechanical properties and a highly oriented texture in thisfilms exhibiting a high critical current density.

Wires and cables of the ceramic materials are usually made from molded,extruded, or compressed polycrystalline powders. The flow of currentbetween the polycrystalline grains is limited by boundaries betweengrains that act as "weak links" and the grains' directional anisotropy,or nonuniformity, with respect to current flow in the crystal. Currentflow is impeded when it must follow a wandering path through randomlyoriented grains. Aligning the grains can help to increase thecurrent-carrying capacity of the ceramic material.

A significant problem with currently available thick oxide materials istheir behavior in applied magnetic fields. Superconductors are eitherType I or Type II materials. Both types exclude magnetic fields and aresuperconducting until a critical field level is reached. Above thislevel, Type I materials become nonsuperconducting. Type II materials,however, continue too superconduct, but allow magnetic flux to penetrateportions of the crystal lattice. Only when an upper critical field isreached do the Type II materials become nonsuperconducting. Mosthigh-temperature superconductors are Type II materials.

Although the new superconductors have extremely high upper criticalfield limits, the "flux lattice," which is how the magnetic fieldspenetrate the superconductor, is unstable. Unless the flux lattice is"pinned," magnetic forces from circulating currents act on the magneticfield lines and cause the flux lattice to move. This movement, or fluxcreep, creates resistance to current flow.

It is generally believed that, because thin films of the materials cancarry large currents, flux creep is not an intrinsic property of oxidesuperconductors material. There is a need to be able to manufacturefilm, particularly thin films and to be able to control boundariesbetween grains. There is a need to be able to manufacture film,particularly thin films and to be able to control boundaries betweengrains.

The above conventional sintering processes are examples of processes inwhich the oxides are generally formed first, particularly as powders,followed by sintering on flat and or smooth powder accessible surfaces.

There are significant limitations inherent in the prior art processes.For example the processes are generally based upon conventional ceramicprocesses and the use of oxide precursor powders and forming. Powdersare consolidated themselves or deposited on a substrate followed bycompaction and sintering. These limitations are particularly apparentfor the processing of non-flat surfaces and where coating uniformly andreduced grain boundary deleterious effects are essential. For example,particularly with non-flat surfaces, portions of a substrate,particularly internal surfaces, which are shielded from the copper oxidepowder e.g., such as pores which extend inwardly from the externalsurface and substrate layers which are internal at least partiallyshielded from the depositing copper oxide source by one or more otherlayers or surfaces closer to the external substrate surface beingcoated, or because of such external surfaces closer proximity to asource system do not get uniformly coated, if at all, in solid/solidtype of sintering processes. Such shielded substrate portions either arenot being contacted by the powder source during processing or are beingcontacted, if at all, not uniformly by the powder source duringprocessing and/or the processing time required is excessive or theprocess not applicable to continuous productions.

Although the sintering process is useful for coating a single flatsurface, for the reasons noted above this process tends to producenon-uniform and/or discontinuous coatings on three dimensional surfaceshaving inner shielded surface and/or the processing is difficult or timeconsuming. Such non uniformities and/or processing drawbacks aredetrimental to the electrical and chemical properties of the coatedsubstrate.

A new process, e.g., a "non-line-of-sight" or "three dimensional"process, useful for coating such substrates would be advantageous. Asused herein, a "non-line-of-sight" or "three dimensional" process is aprocess which coats surfaces of a substrate with conductive copper oxidewhich surfaces would not be directly exposed to copper oxide-formingcompounds being deposited on the external surface of the substrateduring the first contacting step and/or which improves the overallprocessability to conductive component and article and/or type ofsubstrate to be coated. In other words, a "three dimensional" processcoats coatable substrate surfaces which are at least partially shieldedby other portions of the substrate which are closer to the externalsurface of the substrate during processing, e.g., the surfaces of theinternal fibers of a porous mat of ceramic fibers and/or improve theoverall processability from a time and/or type of substrate processingstandpoint.

SUMMARY OF THE INVENTION

A new process for at least partially coating a substrate with a copperoxide-forming material has been discovered. In brief, the processcomprises contacting the substrate with a copper oxide precursor, forexample, cuprous chloride, in a vaporous form and/or in a liquid formand/or in a solid (e.g., powder) form, to form a copper oxideprecursor-containing coating, for example, a cuprous chloride-containingcoating, on the substrate; preferably contacting the substrate with anadditional conductivity forming component, i.e., a component containingfor example a yttrium oxide, barium oxide precursor and/or oxide (as ina compound), to form a multi component-containing coating on thesubstrate; and contacting the coated substrate with an oxidizing agentto form a copper oxide-containing, coating on the substrate. Thecontacting of the substrate with the copper oxide precursor and with theadditional conductivity interacting component can occur together, i.e.,simultaneously, and/or in separate steps. One of the preferredsubstrates for use as conductive particularly superconductors, fibersand particulate are metal and ceramic particulate and/or fibers inparticular copper and magnesia and/or yttrium oxide stabilized zirconiaparticulate and/or fiber.

This process can provide coated substrates which have substantialelectrical conductivity so as to be suitable for use as components inapplication for super conducting materials.. Substantial coatinguniformity, e.g., in the thickness of the copper oxide-containingcoating and in the distribution of the additional component in thecoating, is obtained. Further, the present copper oxide coatedsubstrates have outstanding stability, e.g., in terms of electricalproperties and morphology, and are thus useful in various applications.In addition, the process is efficient in utilizing the materials whichare employed to form the coated substrate.

DETAILED DESCRIPTION OF THE INVENTION

In one broad aspect, the present coating process comprises contacting asubstrate with a composition comprising a copper oxide precursor, suchas copper chloride forming components, including cupric chloride,cuprous chloride and mixtures thereof, preferably cuprous chloride, atconditions, preferably substantially non-deleterious oxidizingconditions, more preferably in a substantially inert environment oratmosphere, effective to form a copper oxide precursorcontainingcoating, such as a cuprous chloride-containing coating, on at least aportion of the substrate. The substrate is preferably also contactedwith at least one preferably two to three conductivity interactingcomponents, such as at least one each of yttrium and barium oxideprecursor and/or oxide components, at conditions, preferablysubstantially non-deleterious oxidizing conditions, more preferably in asubstantially inert atmosphere, effective to form a multicomponent-containing coating, such as a 1,2,3Y,Ba₂, Cu₃ O₇ and/or a1,2,4 component-containing coating, on at least a portion of thesubstrate. This substrate, including one or more coatings containingcopper oxide precursor, for example copper chloride and preferablycuprous chloride, and such additional conductivity interactingcomponents, are contacted with at least one oxidizing agent atconditions effective to convert the copper oxide precursor to copperoxide and form a copper oxide-containing, coating, preferably a yttrium,barium, copper oxide-containing 1,2,3 coating on at least a portion ofthe substrate. By "nondeleterious oxidation" is meant that the majorityof the oxidation of copper oxide precursor, for example cuprouschloride, coated onto the substrate takes place in the oxidizing agentcontacting step of the process, after distribution, and/or equilibrationof the copper oxide precursor rather than in process step or stepsconducted at non-deleterious oxidizing conditions. The process as setforth below will be described in many instances with reference tocuprous chloride, which has been found to provide particularlyoutstanding process and product properties. However, it is to beunderstood that other suitable copper oxide precursors are includedwithin the scope of the present invention.

The additional conductivity interacting components in the coating as setforth above may be applied to the substrate before and/or after and/orduring the time the substrate is coated with cuprous chloride. In aparticularly useful embodiment, the cuprous chloride and the additionalconductivity forming component are both present in the same compositionused to contact the substrate so that the cuprous chloride-containingcoating further contains such additional components. This embodimentprovides processing efficiencies since the number of process steps isreduced (relative to separately coating the substrate with cuprouschloride and conductivity interacting component). In addition, therelative amount of cuprous chloride and conductivity interactingcomponent used to coat the substrate can be effectively controlled inthis "single coating composition" embodiment of the present invention.

In another useful embodiment, the substrate with the cuprouschloride-containing coating and the additional component-containingcoating is maintained at conditions, preferably at substantiallynon-deleterious oxidizing conditions for example condition which allowsfor formation and/or distribution of a copper oxide precursor coatingmore uniformly on the substrate, for a period of time effective to do atleast one of the following: (1) coat a larger portion of the substratewith cuprous chloride-containing coating; (2) distribute the cuprouschloride coating over the substrate; (3) make the cuprouschloride-containing coating more uniform in thickness; and (4)distribute the additional conductivity interacting components moreuniformly in the cuprous chloride-containing coating. Such maintainingpreferably occurs for a period of time in the range of about 0.1 minuteto about 20 minutes in the presence of an inert gas or oxygen if airunder substantially non deleterious oxidizing conditions is used. Suchmaintaining is preferably conducted at the same or a higher temperaturerelative to the temperature at which the substrate/cuprouschloridecontaining composition contacting occurs. Such maintaining, ingeneral, acts to make the coating more uniform and, thereby, forexample, provides for beneficial electrical conductivity properties. Thethickness of the copper oxide-containing coating is preferably in therange of about 0.1 micron to about 100 microns, more preferably about1.0 micron to about 10 microns.

The cuprous chloride which is contacted with the substrate is in avaporous phase or state, or in a liquid phase or state, or in a solidstate or phase (powder) at the time of the contacting. The compositionwhich includes the cuprous chloride preferably also includes theconductivity interacting component or components. This composition mayalso include one or more other materials, e.g., dopants, catalysts,grain growth inhibitors, solvents, etc. crystallization control agents,which do not substantially adversely promote the premature hydrolysisoxidation of the cuprous chloride and/or the additional components, anddo not substantially adversely affect the properties of the finalproduct, such as by leaving a detrimental residue in the final productprior to the formation of the copper oxide-containing coating. Thus, ithas been found to be important, e.g., to obtaining a copper oxidecoating with good structural and/or electronic properties, that unduepremature hydrolysis oxidation of the cuprous chloride and additionalcomponents be avoided.

It has also been found that the substrate can first be contacted with acopper oxide precursor powder, particularly cuprous chloride powder,preferably with a film forming amount of such powder, followed byincreasing the temperature to the liquidus point of the powder on thesubstrate and maintaining the coated substrate for a period of time atconditions including the increased temperature effective to do at leastone of the following: (1) coat a larger portion of the substrate withthe copper oxide precursorcontaining coating; (2) distribute the coatingover the substrate; and (3) make the coating more uniform in thickness.Preferably, this step provides for the equilibration of the coating onthe substrate. The size distribution of the powder, for example, cuprouschloride powder, and the amount of such powder applied to the substrateare preferably chosen so as to distribute the coating over substantiallythe entire substrate.

The copper oxide precursor powder can be applied to the substrate as apowder, particularly in the range of about 5 or about 10 to about 125microns in average particle size, the size in part being a function ofthe substrate particle size, i.e. smaller particles generally requiresmaller size powder. The powder is preferably applied as a chargedfluidized powder, in particular having a charge opposite that of thesubstrate or at a temperature where the powder contacts and adheres tothe substrate. In carrying out the powder coating, the coating systemcan be, for example, one or more electrostatic fluidized beds, spraysystems having a fluidized chamber, and other means for applying powder,preferably in a film forming amount. The amount of powder used isgenerally based on the thickness of the desired coating and incidentallosses that may occur during processing. The powder process togetherwith conversion to a copper oxide-containing coating can be repeated toachieve desired coating properties, such as desired gradientconductivities.

Typically, the fluidizing gaseous medium is selected to be compatiblewith the copper oxide precursor powder, i.e., to not substantiallyadversely affect the formation of a coating on the substrate duringmelting and ultimate conversion to a copper oxide-containing film.

Generally, gases such as air, nitrogen, argon, helium and the like, canbe used, with air being a gas of choice, where no substantial adverseprehydrolysis and or oxidation reaction of the powder precursor takesplace prior to the oxidation-reaction to the copper oxide coating aspreviously discussed under equilibration and maintaining. The gas flowrate is typically selected to obtain fluidization and charge transfer tothe powder. Fine powders require less gas flow for equivalentdeposition. It has been found that small amounts of water vapor enhancecharge transfer. The temperature of the powder precursor is generally inthe range of about 0° C. to about 100° C., or higher more preferablyabout 20° C. to about 40° C., and still more preferably about ambienttemperature. The substrate however can be at a temperature the same asor substantially higher than the powder.

The time for contacting the substrate with precursor powder is generallya function of the substrate bulk density, thickness, powder size and gasflow rate. The particular coating means is selected in part according tothe above criteria, particularly the geometry of the substrate. Forexample, particles, spheres, flakes, short fibers and other similarsubstrate, can be coated directly in a fluidized bed themselves withsuch substrates being in a fluidized motion or state. For fabrics,single fibers and rovings or tows a preferred method is to transport thefabric and/or roving directly through a fluidized bed for powdercontacting. In the case of rovings, and tows a fiber spreader can beused which exposes the filaments within the fiber bundle to the powder.The powder coating can be adjusted such that all sides of the substratefabric, roving and the like are contacted with powder. Typicalcontacting time can vary from seconds to minutes, preferably in therange of about 1 second to about 120 seconds, more preferably about 2seconds to about 30 seconds.

Typical copper oxide precursor powders are those that are powders atpowder/substrate contacting conditions and which are liquidus at themaintaining conditions, preferably equilibration conditions, of thepresent process. It is preferred that the powder on meltingsubstantially wets the surface of the substrate, preferably having a lowcontact angle formed by the liquid precursor in contact with thesubstrate and has a relatively low viscosity and low vapor pressure atthe temperature conditions of melting and maintaining, preferablymelting within the range of about 100° C. to about 650° C., morepreferably about 435° C. to about 630° C. Typical powder copper oxideprecursors are cuprous chloride, cuprous oxide low molecular weightorganic salts or complexes of copper, particularly low molecular weightorganic salts and complexes including poly functional/carboxyl, hydroxyland ketone such as cuprous acetate and acetylacetonate complexes ofcopper.

An additional component powder, such as the conductivity formingadditional powders, can be combined with the copper oxide precursorpowder. The particularly preferred additional powders are yttriumchloride and/or oxide, barium carbonate and/or oxide or peroxide.Further, additional components can be incorporated into the coatingduring the maintaining step, for example a gas as a source of suchadditional component. A combination of the two methods can also be usedfor additional component incorporation.

As set forth above, the copper oxide presursor powders and additionalcomponent conductivity interacting component can produce a film formingamount precursor component on the substrate, particularly distributionof the film over a substantial part of said substrate, followed byoxidation. In addition to the precursor components set forth above,nitrates, sulfates and their hydrates, as well as the hydrator of forexample chloride, can be selected and used within the processingrequirements for producing such conductive films.

The powder copper oxide precursor on melting is maintained and/orequilibrated as set forth above. In addition, temperatures can beadjusted and/or a component introduced into the melting/maintaining stepwhich can aid in altering the precursor for enhanced conversion tocopper oxide. For example, gaseous hydrogen chloride can be introducedto form partial or total halide salts and/or the temperature can beadjusted to enhance decomposition of, for example, copper organic saltsand/or complexes to more readily oxidizable copper compounds. Theadditional interacting component can also be present as an oxideprecursor or in the melt as a dispersed preferably as a finely dispersedsolid. The oxide can be advantageously incorporated as part of thesubstrate powder coating.

A fluidizable coated substrate, such as substrates coated directly in afluid bed of powder, can be subjected to conditions which allow liquidusformation by the copper oxide precursor and coating of the substrate. Aparticularly preferred process uses a film forming amount of the copperoxide precursor which allows for coating during the liquidus step of theprocess, and which substantially reduces detrimental substrateagglomeration. The conditions are adjusted or controlled to allowsubstantially free substrate fluidization and transport under theconditions of temperature and bed density, such as dense bed density tolean bed density. The coated substrate can be further transported to theoxidation step for conversion to copper oxide. A particularly preferredembodiment is the transport of the liquidus coated substrate as a densebed to a fluidized oxidation zone, such zone being a fluidized zonepreferably producing a conversion to copper oxide on the substrate of atleast about 60% by weight, preferably about 80% by weight.

The cuprous chloride and/or conductivity interacting component to becontacted with the substrate may be present in a molten state. Forexample, a melt containing molten cuprous chloride and/or additionalcomponents may be used. The molten composition may include one or moreother materials, having properties as noted above, to produce a mixture,e.g., a eutectic mixture, having a reduced melting point and/or boilingpoint. The use of molten cuprous chloride and/or additional componentprovides advantageous substrate coating while reducing the handling anddisposal problems caused by a solvent. In addition, the substrate isvery effectively and efficiently coated so that coating material lossesare reduced.

The cuprous chloride and/or dopant-forming component to be contactedwith the substrate may be present in a vaporous and/or atomized state.As used in this context, the term "vaporous state" refers to both asubstantially gaseous state and a state in which the cuprous chlorideand/or additional component are present as drops or droplets and/or mistand/or solid dispersions such as colloidal dispersion in a carrier gas,i.e., an atomized state. Liquid state cuprous chloride and/or additionalcomponent may be utilized to generate such vaporous state compositions.

In addition to the other materials, as noted above, the compositioncontaining cuprous chloride and/or the conductivity interactingcomponent may also include one or more grain growth inhibitor and/orcrystallization control components. Such inhibitor component orcomponents are present in an amount effective to inhibit grain growth orprovide optimum crystal orientation in the copper oxide-containingcoating. Reducing grain growth and providing optimum crystal orientationleads to beneficial coating properties, e.g., higher electricalconductivity, more uniform morphology, and/or greater overall stability.Among useful grain growth inhibitor components are components whichinclude at least one metal, in particular calcium, magnesium, siliconand mixtures thereof. Of course, such grain growth inhibitor componentsshould have no substantial detrimental effect on the final product.

The additional components may be deposited on the substrate separatelyfrom the cuprous chloride, e.g., before and/or during and/or after thecuprous chloride/substrate contacting. If the additional component isdeposited on the substrate separately from the cuprous chloride, it ispreferred that the additional component, for example, the conductivityinteracting oxide precursor component, be deposited before the cuprouschloride.

Any suitable conductivity compatible and/or enhancing component may beemployed in the present process. Such conductivity interacting componentshould provide sufficient stoichiometry so that the final copper oxidecoating has the desired properties, e.g., electronic conductivity,stability, etc. Chloride, nitrate, sulfate, organic complexes as setforth above and their hydrate components are particularly usefuladditional components with oxide, peroxide and carbonates being alsouseful. Care should be exercised in choosing the additional component orcomponents for use. For example, the components should be sufficientlycompatible with the cuprous chloride so that the desired conductivecopper oxide coating can be formed. Additional components which haveexcessively high boiling points and/or are excessively volatile(relative to cuprous chloride), at the conditions employed in thepresent process, are not preferred since, for example, the final coatingmay not have requisite stoichiometry and/or a relatively large amount ofthe additional component or components may be lost during processing. Itmay be useful to include one or more property altering components, e.g.,boiling point depressants, in the composition containing the additionalcomponent to be contacted with the substrate. Such property alteringcomponent or components are included in an amount effective to alter oneor more properties, e.g., boiling point, of the additional component,e.g., to improve the compatibility or reduce the incompatibility betweenthe additional component and cuprous chloride.

The use of an additional component is an important feature of certainaspects of the present invention. First, it has been found that suchcomponents can be effectively and efficiently incorporated into thecopper oxide-containing coating. In addition, such additional componentsact to provide copper oxidecontaining coatings with excellent electronicproperties referred to above, morphology and stability.

The liquid, e.g., molten, composition which includes cuprous chloridemay, and preferably does, also include tone or more additionalcomponents. In this embodiment, the additional component or componentsare preferably soluble and/or dispersible in the composition. Atomizedmixtures of cuprous chloride and additional components may also be used.Such compositions are particularly effective since the amount ofadditional component in the final copper oxide coating can be controlledby controlling the make-up of the composition. In addition, both thecuprous chloride and additional component are deposited on the substratein one step. Moreover, if cuprous chloride and yttrium chloride, and abarium oxide precursor (dispersed) are used, such components provide theconductivity stoichiometry and are converted to copper oxide during theoxidizing agent/substrate contacting step. This enhances the overallutilization of the coating components in the present process.Particularly useful compositions produce a yttrium to barium to copperoxide ratio of 1,2,3 or 1,2,4.

As set forth above, a preferred close of superconductors are the 1, 2, 3and 1, 2, 4 superconductors of yttrium, barium and copper. In addition,thallium, barium Ca and copper oxide in an atomic weight ratio of about2, 2, 2,³ are also preferred. Bismuth based copper oxide conductors arefurther examples of conductors within the scope of this invention. Thefilms prepared by the process of this invention enhance the currentcarrying capability of the conductors, can reduce grain boundary currentcarry effects or provide improved control of oxidation and/or annealingconditions and uniformity, including the requisite atomic weightstoichiometry.

The substrates can vary widely as set forth above and under thesubstrate description for application within the scope of thisinvention, such as under catalysts applications. Typical examples ofadditional supports which find usefulness in the process and products ofthis invention include silver, nickel, copper, alumina, includingsapphire, alumina silicate, alumina silica, alumina silica boria,beryllia, magnesia, magnesium alumina silicate and other spinels,yttria, magnesia and zirconia, stabilized zirconia, fosterite, siliconcarbide and nitride and sialon. As set forth above, supports which canproduce substantially detrimental interference and/or reaction with thefilm can be used in combination with means to reduce such effects, suchas barrier conductive films prior to processing of the conduction films.

In one embodiment, a "vaporous" cuprous chloride composition is utilizedto contact the substrate, and the composition is at a higher temperaturethan is the substrate. The make-up of the vaporous cuprouschloride-containing composition is such that cuprous chloridecondensation occurs on the cooler substrate. If one or more additionalcomponents are present in the composition, it is preferred that suchadditional components also contact the substrate. The amount ofcondensation can be controlled by controlling the chemical make-up ofthe vaporous composition and the temperature differential between thecomposition and the substrate. This "condensation" approach veryeffectively coats the substrate to the desired coating thickness withoutrequiring that the substrate be subjected to numerous individual orseparate contactings with the cuprous chloride-containing composition.

The substrate including the cuprous chloridecontaining coating and theconductivity interacting component-containing coating is contacted withan oxidizing agent at conditions effective to convert cuprous chlorideto copper oxide, and form a copper oxide coating on at least a portionof the substrate. Water, e.g., in the form of a controlled amount ofhumidity, can be present during the coated substrate/oxidizing agentcontacting provided that substantial deleterious changes in final copperoxide preferably are controlled and/or minimized. The presence of waterduring this contacting has been found to provide a conductive copperoxide coating having excellent electrical conductivity properties.

Any suitable oxidizing agent may be employed, provided that such agentfunctions as described herein. Preferably, the oxidizing agent (ormixtures of such agents) is substantially gaseous at the coatedsubstrate/oxidizing agent contacting conditions. The oxidizing agentpreferably includes reducible oxygen, i.e., oxygen which is reduced inoxidation state as a result of the coated substrate/oxidizing agentcontacting. More preferably, the oxidizing agent comprises molecularoxygen, either alone or as a component of a gaseous mixture, e.g., air.

The substrate may be composed of any suitable material and may be in anysuitable form. Preferably, the substrate is such so as to minimize orsubstantially eliminate detrimental substrate coating reaction and/ormigration of ions and other species, if any, from or by the substrate tothe copper oxidecontaining coating which are deleterious to thefunctioning or performance of the coated substrate in a particularapplication. However, controlled substrate reaction which provides therequisite stoichiometry can be used and such process is within the scopeof this invention. In addition, the substrate can be precoated tominimize migration, for example an aluminum or silica precoat and/or toimprove wetability and uniform distribution of the coating materials onthe substrate. Further the copper oxide component article can be furthercoated with a barrier film, organic and/or inorganic to minimizereaction of components such as corrosive gaseous components with thefinal copper oxide components article. In order to provide forcontrolled electrical superconductivity in the copper oxide coating, itis preferred that the substrate be substantially non-deleteriousreactive with the copper oxide coating, such as to not changesuperconductive to conductive properties. In the preferred embodiment,the substrate is inorganic, for example metal and/or ceramic. Althoughthe present process may be employed to coat two dimensional substrates,such as substantially flat surfaces, it has particular applicable tocoating three dimensional substrates. Thus, the present process providessubstantial process advances as a three dimensional process. Examples ofthree dimensional substrates which can be coated using the presentprocess include spheres, such as having a diameter of from about 1micron to about 500 microns preferably about 10 microns to about 150microns, extrudates, flakes, single fibers, fiber rovings, choppedfibers, fiber mats, porous substrates, irregularly shaped particles,e.g., catalyst supports, multi-channel monoliths, tubes, conduits andthe like. Ceramic and metal fibers, especially continuous fibers, areparticularly useful substrates when the copper oxide coated substrate isto be used as a superconductor.

The conditions at which each of the steps of the present process occurare effective to obtain the desired result from each such step and toprovide a substrate coated with a copper oxide-containing coating. Thesubstrate/cuprous chloride contacting and the substrate/additionalcomponent contacting preferably occur at a temperature in the range ofabout 435° C. to about 630° C., more preferably about 450° C. to about500° C. The amount of time during which cuprous chloride and/ordopant-forming component is being deposited on the substrate depends ona number of factors, for example, the desired thickness of the copperoxide-containing coating, the amounts of cuprous chloride and additionalcomponents available for substrate contacting, the method by which thecuprous chloride and additional components are contacted with thesubstrate and the like. Such amount of time is preferably in the rangeof about 0.5 minutes to about 20 minutes, more preferably about 1 minuteto about 10 minutes.

If the coated substrate is maintained in a substantially non-deleteriousoxidizing environment, as previously set forth it is preferred that suchmaintaining occur at a temperature in the range of about 435° C. toabout 630° C., more preferably about 450° C. to about 500° C. for aperiod of time in the range of about 0.1 minutes to about 20 minutes,more preferably about 1 minute to about 10 minutes. The coatedsubstrate/oxidizing agent contacting preferably occurs at a temperaturein the range of about 500° C. to about 900° C., more preferably about700° C. to about 850° C., for a period of time in the range of about 1minute or up to about 4 hours. Additional contacting, i.e. annealing, offrom about 450° C. up to about 650° C. can be used to develop optimumconductor properties. A particular advantage of the process of thisinvention is that the temperatures used for oxidation have been found tobe lower, in certain cases, significantly lower, i.e., 50° to 100° C. oreven up to 200° C. than the temperatures required for conventionalsintering. This is very significant and unexpected, provides for processefficiencies and reduces, and in some cases substantially eliminates,deleterious reactions and/or migration of deleterious elements from thesubstrate to the copper oxide layer. Excessive reaction and/ormigration, e.g., from or by the substrate, can reduce electronicconductivity depending on the substrate processing conditions. Inaddition, the oxidizing and/or sintering steps can be combined with astaged oxygen annealing step to develop optimum properties for examplelow to high or high to low concentrations of oxygen.

The pressure existing or maintained during each of these steps may beindependently selected from elevated pressures (relative to atmosphericpressure), atmospheric pressure, and reduced pressures (relative toatmospheric pressure). Slightly reduced pressures, e.g., less thanatmospheric pressure and greater than about 8 psia and especiallygreater than about 11 psia, are preferred.

The potential applications for superconducting materials includelarge-scale, passive application such as shields or waveguides,superconductors screen or reflect electromagnetic radiation and usesrange from coatings on microwave cavities to shielding againstelectromagnetic pulses and bearings. Repulsive forces of superconductorsexcluding magnetic fields provide for noncontact bearings.

In addition, high-current, high-field, applications include magneticimaging/scientific equipment, such as, Superconducting magnets fornuclear magnetic resonance and imaging spectrometers and particleaccelerators; Magnetic separation, such as, magnets used for separationand purification of steel scrap, clays, ore streams, stack gases, anddesulfurizing coal.

Magnetic levitation such as high-speed train systems; electromagneticlaunch systems which can accelerate objects at high velocity. Possibleuses include rapidly repeatable, i.e., earth satellite launching,aircraft catapults, and small guns for military uses.

Other magnet applications include powerful magnets in compactsynchrotrons for electronic thin-film lithography, crystal growth,magnetohydrodynamic energy conversion systems, and ship propulsion bysuperconducting motors or by electromagnetic fields. Other high currenthigh field applications include electric power transmission, such as,transmission cables, carrying more current than conventional conductorswithout loss. Such conductors must be mechanically rugged and operateunder high field and high current conditions; energy storage, such as,large superconducting magnetic coils buried in the ground that can storevast amounts of electrical energy, without power loss, in persistent,circulating currents; load leveling for utilities and as power sourcesfor military systems such as pulsed lasers; generators and motors, suchas, low-temperature system operating with liquid helium. Motors can beused in ship propulsion, railway engines, and helicopters.

In the area of electronics; applications include passive devices, suchas, high-speed wire interconnects in electronic circuits. digitaldevises, such as, superconducting components, based on Josephsonjunctions, to be used as switches or in computer logic and memory. Inaddition, the potential for hybridized semiconductor/superconductorelectronic devices may provide yet unknown applications and devices;sensors, such as, superconducting quantum interference devices, SQUIDs)made from Josephson junctions which are extremely sensitive detectors ofelectromagnetic signals. Low-temperature SQUIDs are used in biomedical,geophysical, and submarine or airplane detection, infrared and microwavesensors.

Other devices include analog-to-digital convertors, voltage standards,signal processors, microwave mixers, filters, and amplifiers.

The copper oxide coated substrate, such as the 1,2,3 and 1,2,4 copperoxide coated substrate, of the present invention may be, for example, acomponent itself or a component of a composite together with one or morematrix materials. The composites may be such that the matrix material ormaterials substantially totally encapsulate or surround the coatedsubstrate, or a portion of the coated substrate may extend away from thematrix material or materials.

Any suitable matrix material or materials may be used in a compositewith the copper oxide coated substrate. Preferably, the matrix materialcomprises a polymeric material, e.g., one or more synthetic polymers,more preferably an organic polymeric material. The polymeric materialmay be either a thermoplastic material or a thermoset material. Amongthe thermoplastics useful in the present invention are the polyolefins,such as polyethylene, polypropylene, polymethylpentene and mixturesthereof; and poly vinyl polymers, such as polystyrene, polyvinylidenedifluoride, combinations of polyphenylene oxide and polystyrene, andmixtures thereof. Among the thermoset polymers useful in the presentinvention are epoxies, phenol-formaldehyde polymers, polyesters,polyvinyl esters, polyurethanes, melamine-formaldehyde polymers, andurea-formaldehyde polymers.

In order to provide enhanced bonding between the copper oxide coatedsubstrate and the matrix material, it has been found that the preferredmatrix materials have an increased polarity, as indicated by anincreased dipole moment, relative to the polarity of polypropylene.Because of weight and strength considerations, if the matrix material isto be a thermoplastic polymer, it is preferred that the matrix be apolypropylene-based polymer which includes one or more groups effectiveto increase the polarity of the polymer relative to polypropylene.Additive or additional monomers, such as maleic anhydride, vinylacetate, acrylic acid, and the like and mixtures thereof, may beincluded prior to propylene polymerization to give the productpropylene-based polymer increased polarity. Hydroxyl groups may also beincluded in a limited amount, using conventional techniques, to increasethe polarity of the final propylene-based polymer.

Thermoset polymers which have increased polarity relative topolypropylene are more preferred for use as the present matrix material.Particularly preferred thermoset polymers include epoxies,phenol-formaldehyde polymers, polyesters, and polyvinyl esters.

Various techniques, such as casting, molding and the like, may be usedto at least partially encapsulate or embed the copper oxide coatedsubstrate into the matrix material or materials and form composites. Thechoice of technique may depend, for example, on the type of matrixmaterial used, the type and form of the substrate used and the specificapplication involved.

In yet another embodiment, a coated substrate including copper oxide,i.e. electronically conductive copper oxide, and at least one additionalcatalyst component in an amount effective to promote a chemical reactionis formed. Preferably, the additional catalyst component is a metaland/or a component of a metal effective to promote the chemicalreaction. The promoting effect of the catalyst component may be enhancedby the presence of an electrical field or electrical current inproximity to the component. Thus, the copper oxide, preferably on asubstantially non-electronically conductive substrate, e.g., a catalystsupport, can provide an effective and efficient catalyst for chemicalreactions, including those which occur or are enhanced when an electricfield or current is applied in proximity to the catalyst component.Thus, it has been found that the present coated substrates are useful asactive catalysts and supports for additional catalytic components.Without wishing to limit the invention to any particular theory ofoperation, it is believed that the outstanding stability, e.g., withrespect to electronic properties and/or morphology and/or stability, ofthe present copper oxides plays an important role in making useful andeffective catalyst materials particularly the higher surface areaattainable of copper oxide materials prepared in accordance with thisinvention, especially when compared to prior art sintering processes.Any chemical reaction, including a chemical reaction the rate of whichis enhanced by the presence of an electrical and/or magnetic field orelectrical current as described herein, may be promoted using thepresent catalyst component copper oxide-containing coated substrates. Aparticularly useful class of chemical reactions are those involvingchemical oxidation or reduction. Chemical reactions, e.g., selectiveoxidation, dehydrogenation, such as alkylaromatics to olefins andolefins to dienes, hydrodecyclization, isomerization, ammoxidation, suchas with olefins, aldol condensations using aldehydes and carboxylicacids and the like, selective methane oxidation, to methanol and/orethane/ethylene may be promoted using the present catalyst component,copper oxide-containing coated substrates. It is believed that processseverity is reduced with these catalysts.

Particularly useful chemical reactions as set forth above include theoxidative dehydrogenation of ethylbenzene to styrene and 1-butene to1,3-butadiene; the ammoxidation of propylene to acrylonitrile; aldolcondensation reactions for the production of unsaturated acids, i.e.,formaldehyde and propionic acid to form methacrylic acid andformaldehyde and acetic acid to form acrylic acid; the isomerization ofbutenes; and the oxidation of methane to methanol.

The copper oxide-containing coated substrates of the present inventionmay be employed alone or as a catalyst and/or support in a sensor, inparticular gas sensors. Preferably, the coated substrates includes asensing component similar to the catalyst component, as describedherein. The present sensors are useful to sense the presence orconcentration of a component, e.g., a gaseous component, of interest ina medium, for example, hydrogen, carbon monoxide, methane and otheralkanes, alcohols, aromatics, e.g., benzene, water, etc., e.g., byproviding a signal in response to the presence or concentration of acomponent of interest, e.g., a gas of interest, in a medium. Suchsensors are also useful where the signal provided is enhanced by thepresence of an electrical field or current in proximity to the sensingcomponent. The sensing component is preferably one or more metals ormetallic containing sensing components, for example, platinum,palladium, silver and zinc. The signal provided may be the result of thecomponent of interest itself impacting the sensing component and/or itmay be the result of the component of interest being chemically reacted,e.g., oxidized or reduced, in the presence of the sensing component.

Any suitable catalyst component (or sensing component) may be employed,provided that it functions as described herein. Among the useful metalcatalytic components and metal sensing components are those selectedfrom components of the transition metals, the rare earth metals, certainother catalytic components and mixtures thereof, in particular catalystscontaining gold, silver, copper, vanadium, chromium, tungsten, zinc,indium, antimony, the platinum group metals, i.e., platinum, palladium,iron, nickel, manganese, cesium, titanium, etc. Although metalcontaining compounds may be employed, it is preferred that the metalcatalyst component (and/or metal sensing component) included with thecoated substrate comprise elemental metal and/or metal in one or moreactive oxidized forms, for example, Cr₂ O₃, Ag₂ O, Sb₂ O₄, etc.

The preferred support materials include a wide variety of materials usedto support catalytic species, particularly porous refractory inorganicoxides These supports include, for example, alumina, zirconia, magnesia,boria, phosphate, titania, ceria, thoria and the like, as well asmulti-oxide type supports such as alumina-phosphorous oxide, silicaalumina, zeolite modified inorganic oxides, e.g., silica alumina, andthe like. As set forth above, support materials can be in many forms andshapes, especially porous shapes which are not flat surfaces, i.e., nonline-of-site materials. A particularly useful catalyst support is amulti-channel monoliths such as made from corderite which has beencoated with alumina. The catalyst materials can be used as is or furtherprocessed such as by sintering of powered catalyst materials into largeraggregates. The aggregates can incorporate other powders, for example,other oxides, to form the aggregates.

The catalyst components (or sensing components) may be included with thecoated substrate using any one or more of various techniques, e.g.,conventional and well known techniques. For example, metal catalystcomponents (metal sensing components) can be included with the coatedsubstrate by impregnation; electrochemical deposition; deposition from amolten salt mixture; thermal decomposition of a metal compound or thelike. The amount of catalyst component (or sensing component) includedis sufficient to perform the desired catalytic (or sensing function),respectively, and varies from application to application. In oneembodiment, the catalyst component (or sensing component) isincorporated while the copper oxide is placed on the substrate. Thus, acatalyst material, such as a salt or acid, e.g., a halide and preferablychloride, oxy chloride and chloro acids, e.g., chloro platinic acid, ofthe catalytic metal, is incorporated into the cuprouschloride-containing coating of the substrate, prior to contact with theoxidizing agent, as described herein. This catalyst material can becombined with the cuprous chloride and contacted with the substrate, orit may be contacted with the substrate separately from cuprous chloridebefore, during and/or after the cuprous chloride/substrate contacting.

The preferred approach is to incorporate catalystforming materials intoa process step used to form a copper oxide coating. This minimizes thenumber of process steps but also, in certain cases, produces moreeffective catalysts. The choice of approach is dependent on a number offactors, including the process compatibility of copper oxide andcatalyst-forming materials under given process conditions and theoverall process efficiency and catalyst effectiveness.

The copper oxide/substrate combinations, e.g., the copper oxide coatedsubstrates, of the present invention are useful in other applications aswell. Among these other applications are included porous membranes,resistance heating elements, electrostatic dissipation elements,electromagnetic interference shielding elements, protective coatings andthe like.

In one embodiment, a porous membrane is provided which comprises aporous substrate, preferably an inorganic substrate, and a copperoxide-containing material in contact with at least a portion of theporous substrate. In another embodiment, the porous membrane comprises aporous organic matrix material, e.g., a porous polymeric matrixmaterial, and a copper oxide containing material in contact with atleast a portion of the porous organic matrix material. With the organicmatrix material, the copper oxidecontaining material may be present inthe form of an inorganic substrate, porous or substantially non porous,having a copper oxide-containing coating, e.g., an electronicallyconductive copper oxide-containing coating, thereon including suchsubstrates set forth above under forms, shapes, and catalyst supports.

One particularly useful feature of the present porous membranes is theability to control the amount of copper oxide present to provide forenhanced performance in a specific application, e.g., a specificcontacting process. For example, the thickness of the copperoxide-containing coating can be controlled to provide such enhancedperformance. The coating process of the present invention isparticularly advantageous in providing such controlled coatingthickness. Also, the thickness of the copper oxide-containing coatingcan be varied, e.g., over different areas of the same porous membrane,such as an asymmetric porous membrane. In fact, the thickness of thiscoating can effect the size, e.g., diameter, of the pores. The size ofthe pores of the membrane or porous substrate may vary inversely withthe thickness of the coating. The coating process of the presentinvention is particularly useful in providing this porosity control.

In addition, an electrostatic dissipation/electromagnetic interferenceshielding element is provided which comprises a three dimensionalsubstrate, e.g., an inorganic substrate, having an electronicallyconductive copper oxide-containing coating on at least a portion of allthree dimensions thereof. The coated substrate is adapted and structuredto provide at least one of the following: electrostatic dissipation andelectromagnetic interference shielding including majestic shieldingapplication as set forth above.

A very useful application for the products of this invention is forstatic, for example, electrostatic, dissipation and shielding,particularly for ceramic and polymeric parts, and depending on thereflection absorption required on metallic parts and more particularlyas a means for effecting dissipation including controlled static chargeand dissipation and/or magnetic/electric field absorption in parts, suchas parts made of ceramics and polymers and the like, as describedherein. The present products can be incorporated directly into thepolymer or ceramic and/or a carrier such as a cured or uncured polymerbased carrier or other liquid, as for example in the form of a liquid,paste, hot melt, film and the like. These product/carrier basedmaterials can be directly applied to parts to be treated to improveoverall performance effectiveness. A heating cycle can be used toprovide for product bonding to the parts.

The particular form of the products, i.e., fibers, i.e., short andcontinuous, flakes, particles, mats or the like, is chosen based uponthe particular requirements of the part and its application, with one ormore of flakes, fibers and particles, including spheres, being preferredfor polymeric and sintered in organic parts. In general, it is preferredthat the particle type products of the invention have a largestdimension, for example, the length of fiber or particle or side of aflake, of less than about 1/8 inch, more preferably less than about 1/64inch and still more preferably less than about 1/128 inch. It ispreferred that the ratio of the longest dimension, for example, length,side or diameter, to the shortest dimension of the products of thepresent invention be in the range of about 500 to 1 to about 10 to 1,more preferably about 250 to 1 to about 25 to 1. The concentration ofsuch product or products in the product/carrier and/or mix is preferablyless than about 60 weight %, more preferably less than about 40 weight%, and still more preferably less than about 20 weight %. A particularlyuseful concentration is that which provides the desired performancewhile minimizing one concentration of product in the final article,device or part.

The present copper oxide/substrate combinations and matrixmaterial/copper oxide/substrate combinations, which have at least somedegree of porosity, hereinafter referred to as "porous contactingmembranes" or "porous membranes", may be employed as active componentsand/or as supports for active components in systems in which the copperoxide/substrate, e.g., the copper oxide coated substrate, is contactedwith one or more other components such as in, for example, separationsystems, gas purification systems, filter medium systems, flocculentsystems and other systems in which the conducting stability anddurability of such combinations can be advantageously utilized,especially super conductivity at the temperatures below the Tc of thecopper oxide material. The particular matrix and it's mechanicalproperties are selected for operation at the Tc of the super conductor.

Particular applications which combine many of the outstanding propertiesof the products of the present invention include magnetic separations,porous and electro membrane separations for particle processing,metallurgical separation, chemical processing, bio medical processingand particle separation. For example, various types of solutions can befurther concentrated, e.g., latex concentrated, proteins isolated,colloids removed, salts removed, etc. The separation devices includingmembranes can be used in flat plate, tubular and/or spiral wound systemdesign.

Membranes containing voids that are large in comparison with moleculardimensions are considered porous. In these porous membranes, the poresare interconnected, and the membrane may comprise only a few percent ofthe total volume. Transport, whether driven by pressure, concentration,or electrical potential or field, occurs within these pores. Many of thetransport characteristics of porous membranes are determined by the porestructure, with selectivity being governed primarily by the relativesize of the molecules or particles involved in a particular applicationcompared to the membrane pores. Mechanical properties and chemicalresistance are greatly affected by the nature, composition and structuree.g., chemical composition and physical state, of the membrane.

Commercial micropore membranes have pore dimensions, e.g., diameters, inthe range of about 0.005 micron to about 20 microns. They are made froma wide variety of materials in order to provide a range of chemical andsolvent resistances. Some are fiber or fabric reinforced to obtain therequired mechanical rigidity and strength. The operationalcharacteristics of the membrane ar defined sometimes in terms of themolecules or particles that will pass through the membrane porestructure.

Microporous membranes are often used as filters. Those with relativelylarge pores are used in separating coarse disperse, suspendedsubstances, such as particulate contamination. Membranes with smallerpores are used for sterile filtration of gases, separation of aerosols,and sterile filtration of pharmaceutical, biological, and heat sensitivesolutions. The very finest membranes may be used to separate, e.g.,purify, soluble macromolecular compounds.

Porous membranes also are used in dialysis applications such a removingwaste from human blood (hemodialysis), for separation of biopolymers,e.g., with molecular weights in the range of about 10,000 to about100,000, and for the analytical measurements of polymer molecularweights. Microporous membranes also may be used as supports for verythin, dense skins or a containers for liquid membranes.

The ability of dense membranes to transport species selectively makespossible molecular separation processes such as desalination of water orgas purification, but with normal thicknesses these rates are extremelyslow. In principle, the membranes could be made thin enough that therates would be attractive, but such thin membranes would be verydifficult to form and to handle, and they would have difficultysupporting the stresses imposed by the application. Conversely,microporous membranes have high transport rates but very poorselectivity for small molecules. Asymmetric membranes, for example madeof the present combinations, in which a very thin, dense membrane isplaced in series with a porous substructure are durable and provide highrates with high selectivity. Such asymmetric membranes and the usethereof are within the scope of the present invention.

Examples of applications for porous membranes include: separation offungal biomass particle removal from hot coal gasification products;desalination of sea water; enhancement of catecholamine determination;removal of colloids from high purity deionized water; filtration oftissue homogenates; separation of antigen from antigen-antibody couplein immunoassay; purification of subcutaneous tissue liquid extracts;concentration of solubilized proteins and other cellular products; celldebris removal; concentration of microbial suspensions (microbialharvesting); enzyme recovery; hemodialysis; removal of casein, fats andlactose from whey; concentration of albumen; separation of skimmed milk;removal of hydrocarbon oils from waste water; recovery and recycling ofsewage effluent; recovery of dye stuffs from textile mill wastes;recovery of starch and proteins from factory waste, wood pulp, and paperprocessing; separation of carbon dioxide and methane; and catalyticchemical reactions.

As described above porous membranes can be used in a wide variety ofcontacting systems. In a number of applications, the porous membraneprovides one or more process functions including: filtration,separation, purification, recovery of one or more components, emulsionbreaking, demisting, flocculation, resistance heating and chemicalreaction (catalytic or noncatalytic), e.g., pollutant destruction to anon-hazardous form.

The porous membrane, in particular the substrate, can be predominatelyorganic or inorganic, with an inorganic substrate being suitable fordemanding process environments. Depending upon the application, thecopper oxide film can be provided with a barrier coating on its surfaceto minimize and/or reduce substantial detrimental outside environmentaleffects and/or conditions on the copper oxide surface. The porousorganic-containing membranes often include a porous organic basedpolymer matrix material having incorporated therein a three dimensionalcopper oxide-containing material, more preferably incorporating a 1,2,3and/or 1,2,4 material optionally a catalytic species, in an amount thatprovides the desired function, particularly electrical conductivity,without substantially deleteriously affecting the properties of theorganic polymer matrix material. These modified polymer membranes areparticularly useful in porous membrane and/or electromembrane and/orcatalytic processes.

Examples of polymer materials useful in microporous membranes includecellulose esters, poly(vinyl chloride), high temperature aromaticpolymers, polytetrafluoroethylene, polymers sold by E.I. DuPontCorporation under the trademark Nafion, polyethylene, polypropylene,polystyrene, polyethylene, polycarbonate, nylon, silicone rubber, andasymmetric coated polysulfone fiber. For temperatures below the Tc ofthe copper oxide superconductor, inorganic matrices are particularlyperformed because of their low temperature mechanical properties as setforth below.

A very convenient application for the coating process and products ofthis invention is the production of a controlled coating, e.g, a thincoating of copper oxide-containing material, on an inorganic substrate,particularly a porous inorganic substrate, to produce a porous membrane.The process provides a new generation of membranes: porous membranes forcontacting processes, e.g., as described herein. The selectivity infiltration, particularly ultra and micro filtration, can also beenhanced by applying an electrical and/or magnetic field and/or anelectrical potential to the porous membrane. The electrical field and/orpotential can be obtained using a two electrode electrical system, themembrane including a electronically conductive copper oxide-containingcoating constituting one of the two electrodes (anode or cathode).

Porous multilayer asymmetric electronically conductive inorganicmembranes, produced in accordance with this invention, are particularlyadvantageous for membrane applications. Among the advantages of suchmembranes are: stability at low and high temperature and/or at largepressure gradients, mechanical stability (reduced and even substantiallyno compaction of the membrane under pressure), stability againstmicrobiological attack, chemical stability especially with organicsolvents, steam sterilization at high temperatures, backflush cleaningat pressures of up to 25 atm, and stability in corrosive and oxidationenvironment.

A membrane can be classified as a function of the size of the particles,macromolecules and molecules separated. Micron sized porous ceramics forfiltration processes can be prepared through sintering of appropriatematerials as set forth herein for the manufacture of sensors. However,the preferred process for membrane-based microfiltration,ultrafiltration and reverse osmosis is to provide inorganic layers withultrafine pores and thickness small enough to obtain high flux throughthe membrane, particularly membranes including copper oxide-containingcoatings.

With this type of asymmetric membrane, separation processes are pressuredriven. Another factor is the interaction at the membrane interfacebetween the porous material and the material to be processed. As notedabove, selectivity can be enhanced by applying an electrical field ontothe surface of the membrane. The electrical field is obtained using atwo electrode electrical device; the conductive membrane constitutingone of the two electrodes (anode or cathode--preferably anode). Suchporous membranes can be obtained with one or more electronicallyconductive copper oxide-containing thin layers on a porous substrate.Conductive copper oxide combined with other metal oxide mixtures alsoprovide improved properties for porous membranes and exhibit electronicconductivity, as well as other functions, such as catalysis orresistance heating.

As set forth above, porous membranes with inorganic materials can beobtained through powder agglomeration, the pores being the intergranularspaces. Conflicting requirements such as high flow rate and mechanicalstability can be achieved using an asymmetric structure. Thus, aninorganic porous membrane is obtained by superimposing a thinmicroporous film, which has a separative function, over a thickmacroporous support. For example, conductive copper oxide coating ontothe surface of filter media can be used as well as onto the surface offlat circular alumina plates. Coated alumina membranes supported on theinner part of sintered alumina tubes designed for industrialultrafiltration processes can be used. Tube-shaped supports can be usedwith varying different chemical compositions, such as oxides, carbides,and clays. Coating of a homogeneous and microporous copperoxide-containing layer depends on surface homogeneity of the support andon adherence between the membrane and its support. Superior results canbe obtained with particulate alumina. The inner part of the tube has amembrane comprising a layer, e.g., in the range of about 10 to about 20microns thick, with pores, e.g., having diameters in the range of about0.02 to about 0.2 microns sized for microfiltration purposes. The mainfeature of such a membrane is uniform surface homogeneity allowing forthe copper oxide-containing coating to be very thin, e.g., less thanabout one micron in thickness.

A particularly unique application that relies upon stable electronicconductivity and the physical durability of the products of thisinvention are dispersions of conductive material, such as powders, influids, e.g., hydrocarbons, e.g., mineral or synthetic oils, whereby anincrease in viscosity, to even solidification, is obtained when anelectrical field is applied to the system. These fluids are referred toas "field dependent" fluids which congeal and which can withstand forcesof shear, tension and compression. These fluids revert to a liquid statewhen the electric field is turned off. Applications include dampening,e.g., shock absorbers, variable speed transmissions, clutch mechanisms,etc.

Certain of these and other aspects the present invention are set forthin the following description of the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block flow diagram illustrating a process for producing thepresent coated substrates.

DETAILED DESCRIPTION OF THE DRAWINGS

The following description specifically involves the coating ofcontinuous copper fibers. However, it should be noted that substantiallythe same process steps can be used to coat other substrate forms and/ormaterials, particularly silver, nickel and ceramic fibers.

A process system according to the present invention, shown generally at10, includes a preheat section 12, a coating section 14, anequilibration section 16 and an oxidation/sintering section 18. Each ofthese sections is in fluid communication with the others. Preferably,each of these sections is a separate processing zone or section.

First gas curtain 20 and second gas curtain 22 provide inert gas,preferably nitrogen, at the points indicated, and, thereby effectivelyinsure that preheat section 12, coating section 14 and equilibriumsection 16 are maintained in a substantially inert environment. Firstexhaust 24 and second exhaust 26 are provided to allow vapors to exit orbe vented from process system 10.

Copper fiber, having a plurality of filaments, from substrate source 28are fed to preheat section 12 where the mats are preheated up to amaximum of 375° C. for a time of 1 to 3 minutes at atmospheric pressureto reach thermal equilibrium. These fibers are composed of from 100micron to 1000 micron diameter copper fibers. The fibers areindividually spread up to 6 inches wide. The fibers are fed to processsystem 10 at the rate of about 1 to 5 feet per minute.

The preheated fibers pass to the coating section 14 where the mats arecontacted with an anhydrous mixture of cuprous chloride, yttriumchloride and barium peroxide from raw material source 30. Thiscontacting effects a coating of this mixture on the mats which willprovide a 1,2, 3y, Ba, to copper oxide ratio after sintering.

This contacting may occur in a number of different ways. For example,the CuCl mixture can be combined with nitrogen to form a mist which isat a temperature of from about 25° C. to about 150° C. higher than thetemperature of the fibers in the coating section 14. As this mist isbrought into contact with the fibers, the temperature differentialbetween the fibers and the mist and the amount of the mixture in themist are such as to cause controlled amounts of CuCl, Ycl₃ and BaO₂ tocondense or to form and/or disperse on and coat the fibers.

Another approach is to apply the CuCl mixture in a molten form directlyto the fiber tow in an inert atmosphere. There are several alternativesfor continuously applying the molten mixture to the fibers. Obtainingsubstantially uniform distribution of the mixture on the fibers is a keyobjective. For example, the fibers can be compressed between two rollersthat are continuously coated with the molten mixture. Another option isto spray the molten mixture onto the fibers. The fibers may also bedipped directly into the melt. The dipped fibers may be subjected to acompression roller step, a vertical lift step and/or a vacuum filtrationstep to remove excess molten mixture from the fibers.

Any part of process system 10 that is exposed to CuCl melt or vapor ispreferably corrosion resistant.

In any event, the fibers in the coating section 14 are at a temperatureof up to about 630° C., more preferably up to about 500° C. and thissection is operated at slightly less than atmospheric pressure. If theCuCl coating is applied as a molten melt between compression rollers, itis preferred that such compression rollers remain in contact with thefibers for about 0.1 to about 2 minutes, more preferably about 1 toabout 2 minutes.

After the CuCl coating is applied to the fibers, the fibers are passedto the equilibration section 16. Here, the coated fiber are maintained,preferably at a higher temperature than in coating section 14, in asubstantially inert atmosphere for a period of time, preferably up toabout 10 minutes, to allow the coating to more uniformly distribute overthe fibers. In addition, if additional components are introduced ontothe fibers separate from the cuprous chloride, the time the coated fibermats spend in the equilibration section 16 results in the additionalcomponents becoming more uniformly dispersed or distributed throughoutthe cuprous chloride coating. Further, it is preferred that any vaporand/or liquid which separate from the coated fibers in the equilibrationsection 16 be transferred back and used in the coating section 14. Thispreferred option, illustrated schematically in FIG. 1 by lines 32 (forthe vapor) and 34 (for the liquid) increases the effective overallutilization of CuCl in the process so that losses of this component, aswell as other materials are reduced.

The coated fibers are passed from the equilibration zone 16 into thesintering zone 18 where such fibers are contacted with an oxidizer, suchas an oxygen-containing gas, from line 36. The oxidizer preferablycomprises a mixture of air and rate accelerating quantities of watervapor. This mixture, is contacted with the coated fiber mats atatmospheric pressure at a temperature of about 700° C. to about 850° C.for up to about 1 hour optionally followed by sintering at a temperatureup to about 900° C. Such contacting results in converting the coating onthe fiber mats to a conductive copper oxide coating. The copper oxidecoated fibers product, which exits sintering section 18 via line 38, hasuseful electrical conductivity properties. This product preferably has acopper oxide coating having a thickness in the range of about 1 micronto about 100 microns, and is particularly useful as a component ingenerators and motors. Preferably, the product is substantially free ofcontamination or side reactions (substrate) which are detrimental toelectrical conductivity.

The present process provides substantial benefits. For example, theproduct obtained has a copper oxide coating which has useful properties,e.g., outstanding electrical and/or morphological properties. Thisproduct may be employed in generators and motors, magnetic imaging,shields and waveguides in combination with a metallic catalyst topromote chemical reactions, or alone or in combination with othercomponent to provide sensors. High utilization of cuprous chloride andadditional components are achieved. In addition, high coating depositionand product throughput rates are obtained. Moreover, relatively mildconditions are employed. For example, temperatures within sinteringsection 18 can be significantly less than 950° C. The product obtainedhas excellent stability and durability.

EXAMPLE 1

A substrate made of yttria stabilized zirconia was contacted with amolten mixture containing CuCl, BaO₂ and YCl₃ in a ratio to provide anatomic ratio of Y, Ba, Cu of 1, 2, 3, or 1, 2, 4, in the final product.This contacting occurred at 350° C. in an argon atmosphere at aboutatmospheric pressure and resulted in a coating being placed on thesubstrate.

The coated substrate was then heated to 457° C. and allowed to stand inan argon atmosphere at about atmospheric pressure for about 20 minutes.The coated substrate was then fired at 800° C. for 20 minutes usingflowing, at the rate of one (1) liter per minute, water saturated air atabout atmospheric pressure.

The material was further annealed at 500° C. for 24 hours. This resultedin a substrate having a copper oxide coating with excellent electronicproperties.

The present methods and products, illustrated above, provide outstandingadvantages. For example, the copper oxide coated substrates,particularly thin film prepared in accordance with the present inventionhave improved, i.e., reduced, electronic defects, relative to substratesproduced by prior methods.

EXAMPLE 2

Cuprous chloride powder is applied to multiple fibers of alumina (randommat) in the form of a powder (10 to 125 microns in average particlediameter) shaken from a powder spreading apparatus positioned 2 to about5 feet above the spread multiple filament. An amount of Ycl₃ and BaO₂powder (10 to about 125 microns in average particle diameter) is addeddirectly to the cuprous chloride powder to provide the necessarystoichiometry for the final copper oxide product. The powder-containingmat is placed into a coating furnace chamber at 450° C. and maintainedat this temperature for approximately 20 minutes. During this time adownflow of 9.0 liters per minute of nitrogen heated to 450° C. to 500°C. is maintained in the chamber.

In the coating chamber the cuprous chloride powder melts and wicks alongthe fiber to form a uniform coating. The Ycl₃ is in a finely dispersedform from about 0.2 to about 2 micron for ease of wicking. In addition,a small cloud of cuprous chloride vapor can form above the mat. This isdue to a small refluxing action in which hot cuprous chloride vaporsrise slightly and are then forced back down into the mat for coating anddistribution by the nitrogen downflow. This wicking and/or refluxing isbelieved to aid in the uniform distribution of cuprous chloride andadditional components in the coating chamber.

The fiber is then moved into the oxidation chamber. The oxidation stepoccurs in a molecular oxygen-containing atmosphere at a temperature of800° C. for a period of time of 1 hour. The fiber may be coated by thisprocess more than once to achieve thicker coatings and/or removed andannealed in a finishing oxidation step to develop the optimum crystalstructure for conductivity.

EXAMPLE 3

Example 2 is repeated except that the powder is applied to the mat usinga powder sprayer which includes a canister for fluidizing the powder andprovides for direct injection of the powder into a spray gun. The powderis then sprayed directly on the mat, resulting in a highly uniformpowder distribution.

EXAMPLE 4

Example 2 is repeated except that the powder is applied to the fiber bypulling the mat through a fluidized bed of the powder, which as anaverage particle diameter of about 5 to about 125 microns for meltablecomponents and from about 0.2 to about 2 micron for dispersiblecompounds.

EXAMPLE 5 to 7

Examples 2, 3 and 4 are repeated except that, prior to contacting withthe powder, the mat is charged by passing electrostatically charged airover the mat. The powder particles are charged with an opposite chargeto that of the mat. The use of oppositely charged mat and powder acts toassist or enhance the adherence of the powder to the mat.

EXAMPLES 8 TO 13

In each of the Examples 2 to 7, the final coated mat includes aneffective copper oxide-containing coating having a substantial degree ofuniformity.

While this invention has been described with respect to various specificexamples and embodiments, it is to be understood that the invention isnot limited thereto and that it can be variously practiced within thescope of the following claims.

What is claimed is:
 1. A process for coating an inorganic threedimensional substrate with copper oxide comprising:contacting aninorganic three dimensional substrate which includes external surfacesand shielded surfaces which are at least partially shielded by otherportions of said substrate with a composition comprising a copper oxideforming compound other than copper oxide at conditions effective to forma copper chloride-forming compound containing coating on at least aportion of said substrate; forming a liquidus copper oxide formingcompound containing coating on at least a portion of the threedimensions of said substrate including the shielded surfaces of saidsubstrate; contacting said substrate with at least one additionalmagnetic or conductivity interacting component at conditions effectiveto form a component-containing coating on at least a portion of saidsubstrate including at least a portion of the three dimensions of saidsubstrate including the shielded surfaces of said substrate; saidcontacting being initiated at least prior to the substantially completeoxidation of said copper oxide forming compound to copper oxide; andcontacting said substrate having said copper oxide forming compoundcontaining coating and said additional component-containing coatingthereon with an oxidizing agent at conditions effective to convert saidcopper oxide forming compound to copper oxide and form copper oxidecoating with the additional magnetic or conductivity interactingcomponent on at least a portion of said three dimensions of saidsubstrate including the shielded surfaces of said substrate.
 2. Theprocess of claim 1 wherein said copper oxide forming compound isselected from the group consisting of copper chloride, low molecularweight copper organic salts, low molecular weight copper organiccomplexes and mixtures thereof.
 3. The process of claim 1 wherein saidcopper oxide forming compound is cuprous chloride.
 4. The process ofclaim 1 wherein said additional conductivity interacting component is anoxide precursor selected from the group consisting of yttrium, barium,calcium, thallium and conductivity interacting mixtures.
 5. The processof claim 1 wherein said additional conductivity interacting component isan oxide precursor selected from the group consisting of yttrium andbarium conductivity interacting mixture in a mole ratio with copperoxide of about 1 to about 2 to about 3 up to about 4 and thallium,barium, calcium in a mole ratio with copper of about 1, to about 1, toabout 1 to about 2 up to about
 3. 6. The process of claim 1 wherein saidsubstrate is maintained for a period of time at conditions effective todo at least one of the following: (1) coat a larger portion of saidsubstrate with said copper oxide forming compound: (2) distribute saidcopper oxide forming compound over said substrate; (3) make said copperoxide forming compound-containing coating more uniform in thickness; (4)incorporate said additional conductivity interacting component in saidcopper oxide forming compound coating; and (5) distribute saidadditional conductivity interacting component more uniformly in saidcopper oxide forming compound containing coating.
 7. The process ofclaim 1 wherein said substrate is in a form selected from the groupconsisting of spheres extrudates, flakes, fibers, fiber rovings, choppedfibers, fiber mats, porous substrates, irregularly shaped particles,tubes and multi-channel monoliths.
 8. The process of claim 7 where insubstrate is a material selected from the group consisting of copper,silver, nickel and a ceramic oxide.
 9. A process for coating aninorganic three dimensional substrate with copper oxidecomprising:contacting an inorganic three dimensional substrate whichincludes external surfaces and shielded portions of said substrate witha composition comprising a copper chloride-forming compound atconditions effective to form a copper chloride-forming compoundcontaining coating on at least a portion of said substrate; forming aliquidus copper chloride-forming compound containing coating on at leasta portion of the three dimensions of said substrate including theshielded surfaces of said substrate and at conditions effective to do atleast one of the following: (1) coat a larger portion of said substratewith said copper chloride-forming compound; (2) distribute said copperchloride-forming compound over said substrate; and (3) make said copperchloride-forming compound containing coating more uniform in thickness;and contacting said substrate with said copper chlorideforming compoundcontaining coating with an oxidizing agent at conditions effective toconvert the copper chloride forming compound to copper oxide and form acopper oxide coating on at least a portion of said three dimensions ofsaid substrate including the shielded surfaces of said substrate. 10.The process of claim 9 which further comprises contacting said substratewith an additional magnetic or conductivity interacting component atconditions effective to form an additional component containing coatingon said substrate, said additional component contacting occurring priorto substantially complete oxidation of said copper chloride formingcompound to the oxide.
 11. The process of claim 10 wherein saidsubstrate s in a form selected from the group consisting of spheres,extrudates, flakes, fibers, fiber rovings, chopper fibers, fiber mats,porous substrates, irregularly shaped particles, tubes and multi-channelmonoliths.
 12. The process of claim 11 where in substrate is a materialselected from the group consisting of copper, silver, nickel and aceramic oxide.
 13. The process of claim 9 wherein any one or more ofsaid contacting steps and said is conducted under gas fluidizingconditions.
 14. A process for coating surfaces of an inorganic threedimensional substrate with copper oxide which comprises: contacting aninorganic three dimensional substrate with a composition comprising acopper oxide precursor powder other than copper oxide at conditionseffective to form a coating containing copper oxide precursor on atleast a portion of the substrate; forming a liquidus copper oxideprecursor on at least a portion of the three dimensions of saidsubstrate including the shielded surfaces of said substrate and atconditions effective to do at least one of the following: (1) coat alarger portion of said substrate with said coating containing copperoxide precursor; (2) distribute said coating containing copper oxideprecursor over said substrate; and (3) make said coating containingcopper oxide precursor more uniform in thickness; and contacting saidcoated substrate with an oxidizing agent at conditions effective toconvert said copper oxide precursor to copper oxide on at least aportion of said three dimensions of said substrate and form a substratehaving a copper oxide-containing coating.
 15. The process of claim 14which further comprises contacting said substrate with a additionalmagnetic or conductivity interacting component at conditions effectiveto form a additional component containing coating on said substrate,said additional component contacting occurring prior to thesubstantially complete oxidation of said copper oxide precursor tocopper oxide.
 16. The process of claim 14 wherein said copper oxideforming component is selected from the group consisting of copperchloride, low molecular weight copper organic salts, low molecularweight copper organic complexes and mixtures thereof.
 17. The process ofclaim 14 wherein said copper oxide forming compound is cuprous chloride.18. The process of claim 15 wherein said additional component is anadditional oxide precursor selected from the group consisting ofyttrium, barium, calcium, thallium and conductivity interacting mixturesthereof.
 19. The process of claim 16 wherein said additional componentis an additional oxide precursor selected from the group consisting ofyttrium, barium, calcium, thallium and conductivity interacting mixturesthereof.
 20. The process of claim 14 wherein any one or more of saidcontacting steps and said forming step is conducted under gas fluidizingconditions.
 21. The process of claim 14 wherein said substrate iscontacted with a film forming amount of said copper oxide precursorpowder.
 22. The process of claim 1 wherein said substrate is selectedfrom the group consisting of spheres, extrudates, flakes, fibers, wires,porous substrates, tubes, and irregularly shaped particles.
 23. Theprocess of claim 2 wherein any one or more of said contacting steps andforming step is conducted under gas fluidizing conditions.
 24. Theprocess of claim 10 wherein said copper chloride forming compound iscuprous chloride.
 25. The process of claim 24 wherein said substrate isin a form selected from the group consisting of spheres, extrudates,fibers, wires, tubes, flakes, porous substrates, and irregularly shapedparticles.
 26. The process of claim 9 wherein said copper chlorideforming compound contacting the substrate is in a solid state.
 27. Theprocess of claim 14 wherein said substrate is selected from the groupconsisting of spheres, extrudates, tubes, flakes, fibers, wires, poroussubstrates, and irregularly shaped particles.